Data has become an important asset in almost every application, whether it is a Line-of-Business (LOB) application utilized for browsing products and generating orders, or a Personal Information Management (PIM) application used for scheduling a meeting between people. Applications perform both data access/manipulation and data management operations on the application data. Typical application operations query a collection of data, fetch the result set, execute some application logic that changes the state of the data, and finally, persist the data to the storage medium.
Traditionally, client/server applications relegated the query and persistence actions to database management systems (DBMS), deployed in the data tier. If data-centric logic, it is coded as stored procedures in the database system. The database system operated on data in terms of tables and rows, and the application, in the application tier, operated on the data in terms of programming language objects (e.g., Classes and Structs). With the advent of the web technology (and Service Oriented Architectures) and with wider acceptance of application servers, applications are becoming multi-tier, and more importantly, data is now present in every tier.
In such tiered application architectures, data is manipulated in multiple tiers. In addition, with hardware advances in addressability and large memories, more data is becoming memory resident. Applications are also dealing with different types of data such as objects, files, and XML (eXtensible Markup Language) data, for example.
In hardware and software environments, the need for rich data access and manipulation services well-integrated with the programming environments is increasing. Moreover, serializing entities (e.g., object representation of data) for subsequent use in n-tier Service Oriented Architecture (SOA) can be burdened with inefficiencies. For example, serializing relationship information is not intuitive at the entity abstraction, and it is burdensome to include adequate information for reconstructing the first class relationship.